英语翻译Liquid crystal dimers [1] are composed of moleculescontaining two mesogenic groups linked via a flexiblespacer.They can be sub-divided into two broad groups:symmetric dimers,in which the two mesogenic units areidentical,and non-symmetric

英语翻译Liquid crystal dimers [1] are composed of moleculescontaining two mesogenic groups linked via a flexiblespacer.They can be sub-divided into two broad groups:symmetric dimers,in which the two mesogenic units areidentical,and non-symmetric
英语翻译
Liquid crystal dimers [1] are composed of molecules
containing two mesogenic groups linked via a flexible
spacer.They can be sub-divided into two broad groups:
symmetric dimers,in which the two mesogenic units are
identical,and non-symmetric dimers,which contain two
different mesogenic units [2,3].Initial interest in these
materials stemmed from their use as model compounds
for semi-flexible main chain liquid crystal polymers [4,
5]; they are now of fundamental interest in their own
right due to their unique phase behaviour,and their
smectic polymorphism [1–3] which are significantly
different from those of conventional low molar mass
liquid crystals.
For the majority of symmetric dimers containing
terminal alkyl chains,a simple empirical rule has
emerged relating the occurrence of smectic behaviour
to the molecular structure; specifically,if a symmetric
dimer is to exhibit a smectic phase then the terminal
chain length must be greater than half the spacer length
[1–3,6].This empirical rule effectively eliminates the
possibility that symmetric dimers form an intercalated
structure simply because the terminal chains can only be
accommodated within such a structure if the total
length of the two terminal chains is equal to or less than
that of the spacer [2].Symmetric dimers appear therefore
to have a strong tendency to exhibit monolayer
smectic phases and the driving force for their formation
is the incompatibility between the terminal alkyl chains
and the spacers,leading to a microphase separation into
three regions:terminal chains,mesogenic groups and
flexible alkyl spacers [3].
In contrast,non-symmetric liquid crystal dimers
often exhibit intercalated smectic phases,in which
specific molecular interactions between the two different
mesogenic units account for this specific phase behavior
[1–3,7,8].The question arises,what would happen if
the interaction between the identical mesogenic units in
symmetric dimers increases?To investigate this,we have
designed a series of symmetric liquid crystal dimers
containing a hydrazide group as the mesogenic units
(see scheme 1),in which lateral intermolecular hydrogen
bonding was expected to increase the intermolecular
interaction.Nitro,phenyl,and methyl terminal groups,
instead of long alkyl chains,were used as terminal
substituents to avoid the unfavourable interaction
between the terminal alkyl chains and spacers [2,3].

英语翻译Liquid crystal dimers [1] are composed of moleculescontaining two mesogenic groups linked via a flexiblespacer.They can be sub-divided into two broad groups:symmetric dimers,in which the two mesogenic units areidentical,and non-symmetric
液晶二聚体[1]是由分子
含有两个主要通过灵活.组联系
衬垫.在他们可分为两个主要团体:
对称二聚体,主要是两个单位
相同的,非对称二聚体,含有两个
不同的主要单位[2,3].原初兴趣在这些
材料源自于他们的使用为模型化合物
为semi-flexible主链液晶聚合物[4,
5];他们现在在自己的根本利益
对由于其独一无二的阶段的行为,他们的
[1 - 3]smectic多态性明显
有别于常规低摩尔质量
液晶.
对大多数对称二聚体包含
终端烷基链,一个简单的经验法则
有关smectic出现发生的行为
到分子结构;明确地说,如果一个对称的
二是要揭示一个smectic阶段然后终端
分子链的长度必须大于一半的间隔臂的长度
[1 - 3,6].这个经验规则有效清除
可能形成一个夹层对称二聚体
结构简单,只能终端连锁店
这样一个结构平衡的总数
这两个终端链长度等于或小于
间隔的[2].对称二聚体出现因此
有一个强烈倾向展览单层
smectic阶段形成的动力
是不兼容的终端烷基链呢
和显示,导致microphase离析
三个区域:终端连锁店,主要包括组织和
烷基垫片灵活[3].
相比之下,非对称液晶二聚体
设置smectic阶段经常展出,其中
特定分子的相互作用两种不同的
这一特定的单位账户主要阶段的行为
[1 - 3、7、8].问题出现了,会发生什么事
互动的主要单位相同
对称二聚体增加吗?调查这件事,我们已经有了
设计了一系列对称液晶二聚体
包含一个组织作为主要为单位
(见方案1),在这种侧电子氢
键时将增加
互动.硝基、苯、甲基终端组,
而不是长烷基链,作为终端
为了避免不利的取代基的相互作用
烷基链和终端之间的间隔[2,3].